The phosphorylation of proteins on serine or threonine residues preceding proline (pSer/Thr-Pro motifs), catalized by the peptidyl-prolyl cis/trans isomerase Pin1, has been confirmed as a major cell transformation mechanism activating different oncogenic pathways in many types of human tumours (including thyroid cancer) [9,13,23,24]. The gene discussed is PIN1; the disease is thyroid cancer.